On the ionospheric F2-region equatorial anomaly and the geomagnetic field

A review of the theories concerning the equatorial F2 region ionosphere

“…Awojobi (1965, a, b) followed a similar approach with a slightly modified loss function and concluded that geomagnetic control is not necessary to account for the distribution of the anomaly. This latter conclusion is probably not valid, as pointed out by Ostrow and Stewart (1967) and other works listed herein. I•Iowever, there is no question that temperature can play an important role in influencing the shape of the equatorial distributions and yet, no inclusion of this effect has been offered in any of the causal approach studies.…”

F region

“…The morphology of the equatorial anomaly was discussed by Rush et al [1969] with the aid of topside and bottomside soundings. Ostrow and Stewart [1967] reaffirmed that the equatorial ionosphere is under geomagnetic control. Time dependent calculations by Sterling et al [1969] show that equatorward winds are necessary to maintain the nighttime ionosphere above 10° magnetic latitude and that the equatorial noon biteout is caused by upward drift.…”